The subject matter disclosed herein relates to electrical devices, and more specifically, to techniques suitable for wafer bonding quartz-based devices, including quartz-based surface acoustic wave (SAW) devices.
SAW devices may be used in a variety of applications. For example, in electronic circuits, SAW devices may be used as filters, oscillators, and/or transformers. Additionally, SAW devices may be used as sensors for torque, temperature, pressure, and/or other parameters. Certain processes, such as engine, transmission, and the like, may be more precisely controlled using feedback from the SAW device sensors. To put the SAW devices in this environment they need to be packaged. Typically these packages are hermetic discrete packages that the SAW is placed into and sealed. When putting the SAW into these packages, the sensitivity is reduced, so it is desired to have the SAW mounted directly to the strain point. For this reason a wafer level package is desired. SAW devices may include a piezoelectric material, such as a single crystal quartz wafer, that generates an electrical signal in response to mechanical stress, enabling the detection of acoustic waves. These acoustic waves can be used to determine, for example, the torque of a rotating shaft. However, the properties of single crystal quartz can make bonding difficult when manufacturing a quartz-based package. Further, the single crystal quartz wafer is very thin and, therefore, may break easily when uneven thermal and/or mechanical stress is applied. A process that overcomes these challenges during bonding is desired.